Answer:
C. green is not a function, red is a function
Step-by-step explanation:
A curve does not describe a functional relationship if a vertical line crosses it in more than one place. Clearly the y-axis crosses the green curve in 2 places, so it is NOT a function.
There is a very steep section at x=10 on the red curve. It we assume it is simply "very steep" and not "vertical", then the red curve IS a function. If you assume that short section is vertical, then the red curve is not a function, either. My choice is to go with "very steep," not "vertical."
My conclusion is that green is not a function; red is a function.
